The present invention relates to an improvement in a connector with a steering angle sensor and an improvement in a steering column structure using the same, in which a steering angle sensor is integrated with a steering roll connector (SRC) which is a cable-type electric connection device.
An SRC by which electric signals can be transmitted to a squib on a steering wheel with a high reliability is adopted particularly in vehicles mounted with air-bags. On the other hand, in four-wheel steering cars, so-called steering angle proportional control is performed for steering rear wheels in the reverse phase at a low speed range and in the same phase at a middle or high speed range in proportion to a steering angle. For this control, a steering angle sensor for detecting the steering angle is mounted on the four-wheel steering cars.
FIG. 4 is a sectional view of a conventional steering column portion provided with an SRC and a steering angle sensor, and FIG. 5 is a perspective view of a slit plate of the steering angle sensor. A turn signal and head lamp switch lever 3 and a wiper control switch lever 5 are provided in the outer circumference of a steering column switch (column switch) 1 through a steering shaft. An SRC 7 is provided on the upper side of the column switch 1 (on the upper side of FIG. 4). In the SRC 7, an inner cylinder 11 as a rotating body is provided in the inside of an outer cylinder 9 as a fixed body concentrically therewith. A not-shown cable is stored spirally in an annular storage chamber formed between the outer cylinder 9 and the inner cylinder 11. One end of the cable is supported on the outer cylinder 9 while the other end is supported on the inner cylinder 11. The cable supported on the inner cylinder 11 is led out as a wire harness, and connected to a squib (an electric heater wire charged with a very small amount of explosive) on a steering wheel.
In the thus configured SRC 7, electricity can be supplied to the rotating body (steering wheel) with a higher reliability than that in an electric connection device of sliding contact type in which instantaneous interruption of electric service is produced in the sliding portion.
On the other hand, a steering angle sensor 13 is provided on the lower side of the column switch 1 (on the lower side of FIG. 4). The steering angle sensor 13 is constituted by a slit plate 17 having a plurality of slits 15 (see FIG. 5) provided in its outer edge portion, and a sensor portion 19 holding the outer edge portion of this slit plate 17 from its upper and lower sides. In the steering angle sensor 13, the slit plate 17 is attached to the steering shaft so that the slit plate 17 rotates with the steering shaft, while the sensor portion 19 is fixed to the column switch 1. In the sensor portion 19, a not-shown light emitting means such as a light-emitting diode and a not-shown light receiving means such as a phototransistor are provided so as to be opposite to each other through the outer edge portion of the slit plate 17.
In the steering angle sensor 13, the phototransistor receives light from the light-emitting diode through the slits 15 of the slit plate 17 which rotates in accordance with the steering of a steering wheel, and this light passing through the slits is converted into current pulses and counted by a counter or the like so as to detect the rotation angle of the steering wheel.
However, in the above-mentioned conventional column structure, the SRC 7 is attached to the upper side of the column switch 1 while the steering angle sensor 13 is attached to the lower side of the column switch 1. Therefore, there has been a problem that the size H in the direction of the steering shaft of the column switch 1 is increased, so that it is necessary to ensure a large on-vehicle size for the column switch 1.
In addition, two electric equipments respectively constituted by a rotating body and a fixed body are provided on the same shaft of a steering shaft, so that similar parts are disposed doubly. Therefore, there has been a problem that the number of parts is increased.